Are those smooth or engraved walls in the screenshots?
Smooth walls. Just the object testing arena. Engraved walls start unobscured by default so you can actually see what's been engraved, just as Armok intended.
Anyway, can't wait for the 20x20 version
Most definitely do not want to make it. Honestly, if I had my way I'd stop supporting the graphics set and switch entirely to dwarf letters, stop supporting 20x20 sets or just double them crudely, and stop supporting the "straight" wall variants for all sets. But then nobody would download my tilesets anymore, which is no fun. The whole point of art is to be enjoyed.
I was trying to figure out tile magic engraved walls, but seem to have gotten it backwards.
Too much of a purist to use tile magic: I tried tile magic in 2012 or 2013 to save the barrel graphic, before I started becoming an "ASCII purist". It doesn't work well with color schemes that have non-pure-black backgrounds. I suppose it works reasonably better now that most of my color schemes have almost-black blacks, but there's still a color difference there in your image (#020202 for blackness around walls, #070707 for blackness everywhere else) and that gets more noticeable with Tocky's colors or any of Vherid's colors.
I'm still curious to see what you come up with, though!
EDIT: seriously though, nice job with the quick doubled version. I'd love it if you looked over the 20x20 sets and improved them. They're still far from perfect, IMO.